1. Field of the Invention
The invention relates to roadworking machines and, more particularly, relates to roadworking machines capable of milling at least an upper layer of a roadway surface for transport from a work site or for cold in-place recycling.
2. Discussion of the Related Art
Milling machines are well known for planing the surface of a roadway. One such machine is disclosed in U.S. Pat. No. 4,139,318 to Jakob et al. (the Jakob patent). The milling machine disclosed in the Jakob patent includes a chassis, a planer or milling assembly, and a reclaimer assembly. The planer assembly includes a rotating cutter drum for removing the upper layer of the roadway surface and a floating moldboard which is yieldingly forced into contact with the roadway to the rear of the cutter drum. The reclaimer assembly includes a primary conveyor which extends forwardly from the cutter drum to the front of the chassis and which empties into a secondary conveyor extending forwardly and upwardly from the front of the primary conveyor. The secondary conveyor transports removed roadway materials from the primary conveyor to a dump truck or the like for transport to either 1) a landfill or the like for disposal, or 2) an asphalt plant for recycling.
Cold in-place recycling is becoming increasingly popular for the on-the-spot recycling of roadway paving materials. The typical cold in-place recycling operation involves the removal of the top layer of a roadway surface, the mixing of the removed materials with liquid asphalt, and the depositing of the mixture back onto the roadway surface. The system disclosed by the Jakob patent, while functioning well as a front load road planing machine, is generally thought to be incapable of cold in-place recycling because it is designed to travel forwardly during the milling operation and thus, if used in a cold in-place recycling system, would run over the recycled materials laid down by the system.
A roadworking machine capable of conducting a front load road planing operation and of forming part of a cold in-place recycling system is manufactured by Astec Corporation of Chattanooga, Tenn. under the Model No. RX60. The Astec RX60 machine differs from that disclosed in the Jakob patent primarily in that it has both front and rear moldboard assemblies each of which is independently raisable and lowerable. The rear moldboard is lowered and the front moldboard raised for a front load road planing operation in which the vehicle travels in the reverse direction to discharge materials into a dump truck or the like, and the rear moldboard is raised and the front moldboard lowered for a cold in-place recycling operation in which the vehicle travels in a forward direction to discharge materials into a paving machine in which the materials are mixed with asphalt and/or an aggregate before being deposited onto the roadway surface. This RX60 machine functions well as a front load road planing machine and as part of a cold in-place recycling system using a paving machine in conjunction with the roadworking machine. It is, however, incapable of performing a cold in-place recycling operation without a separate paving machine.
Roadworking machines have been proposed to effect milling and cold in-place recycling in a single operation. One such machine is disclosed in U.S. Pat. No. 4,317,642 to Wirtgen (the Wirtgen patent). The machine disclosed by the Wirtgen patent mills the upper layer of a roadway surface via a rotary drum and feeds the removed materials to a mixer mounted on the vehicle chassis where it is mixed with aggregate. The thus mixed materials are then spread onto the roadway surface and compacted by another machine.
The machine disclosed by Wirtgen suffers from marked drawbacks and disadvantages. For instance, it is incapable of adjusting the position of the mixer with respect to the chassis and thus has limited versatility. The machine disclosed by Wirtgen is also incapable of conversion to a front load road planing machine.